Three things about the fic that I would change.
First thing, Belldandy sounds too much like Jeanie from "I Dream of Jeanie." I
can't see her calling Keiichi "Master" or something like that. And, why couldn't
you use Urd instead of Bell-chan? Isn't love, sex, and bondage right up her
alley?
Second thing is Keiichi is far, far, far shier than you've made him out to be,
and I don't think he'd say he wanted a sex slave right out. If he wanted
something like that, I would have say in a round-about way. Tentatively, and
with more loopholes than a typical tax bill going through the House of
Representatives.
Finally, it looks like you're rushing the pace, causing the action to set up in
a bang-bang style that tired me out and maybe a little too fast for a romantic
lemon comedy.
Otherwise, it's a pretty good fic as it stands.
---Andrew